gen: update due to sdbusplus-gen-meson change

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9491eb608d9c6849b3e39fe212054a3651bfb824
diff --git a/gen/org/open_power/meson.build b/gen/org/open_power/meson.build
index 3f33ebc..b24f5ea 100644
--- a/gen/org/open_power/meson.build
+++ b/gen/org/open_power/meson.build
@@ -6,6 +6,7 @@
     'org/open_power/Host__markdown'.underscorify(),
     input: [ '../../../yaml/org/open_power/Host.errors.yaml',  ],
     output: [ 'Host.md' ],
+    depend_files: sdbusplusplus_depfiles,
     command: [
         sdbuspp_gen_meson_prog, '--command', 'markdown',
         '--output', meson.current_build_dir(),